Bufo alvarius is quite well known to Arizona desert residents. After a monsoon rainstorm, their songs waft through the clean, creosote scented air!
But most people know them by another name. Their nicknames - like the Colorado River Toad, Colorado Bullfrog (although they are NOT a frog), or the Sonoran Desert Toad.
When you live in the Sonoran Desert in Arizona, you will almost certainly encounter them at some point. I remember one time during the Monsoon season, returning home. As we approached our doorstep, there was a huge one right in the desert grasses just to the left of the steps! It must have been the grand-daddy, as it was probably about 10 inches from its snout to its hind area. They are typically more like 7 inches.
We didn't go right inside, but watched it until it hopped away. It was the first time we had seen one, since moving to AZ - but it wasn't to be the last...
Many animal pets have encounters with these toads. Sadly, it doesn't often end well for them. Our daughter's dog, a collie mix, got sick overnight after a storm. She was sadly, dead by morning. We all believe she encountered a Sonoran Desert toad and messed with it somehow. They have a type of venom embedded in the glands of their skin.
A Colorado River toad begins its life somewhere between central Arizona south through the Mexican states of Sonora and to Sinoloa. So it's essentially a resident of the Sonoran Desert, although it is found in adjacent biomes. It's one of the biggest toads in all of North America.
Previously it was known to live in the most Southeastern California desert areas. It hasn't been observed there since about the mid 1950s. That's likely due to farming depleting their habitat. Plus with the effects of pesticides - contributing to their disappearance there.
The Monsoon rains will sponsor their life start. The males start their calls after a good rain storm. Their call is described as weak, especially when compared with other Monsoon responding toads and frogs. But females still seek them out. See what you think of their call - hear it [the weak, low pitch, less than 1 second croak - amidst the others] by clicking here>
The adults mate externally. Meaning eggs are laid by females into large pools of water left by rains. The males fertilize the eggs as they're placed by the females. If more permanent water sources are found, such as ponds, etc. - they use them also.
My daughter found numerous toads, as well as frogs in her backyard pool after a particularly rainy set of Monsoon storm days a number of years back! They had to fish them out with the pool net!!
About 8000 eggs in multiple strings hatch into the initial tadpole form. They spend 10 weeks in this larva-type formation, transforming into a toad. By the 10th week they're now now a young Bufo alvarius. They're beginning their 10 to 20 year life expectation!
There's been a reevaluation of the scientific naming. It may also more recently be seen listed as Incilius alvarius. It's said to be more taxonomically accurate. However the name Bufo alvarius still sticks.
These desert survivalists have figured out how to get through the heat of the day, and through the winter chill-down! They appear to go into a state of torpor - a kind of hibernation state. They find a rodent hole or rock under-cropping area which offers shelter. They hide there from the heat of the day, or when there's dry times occurring day after day.
They can even burrow down into the desert sands to stay moist. One day in my backyard I was digging a hole to plant a tree. It was a number of years ago. But I know the dirt was moist, and it was toward the end of Monsoon season. I dug up a big, chunky Bufo tadpole!
Their active time is from about mid-June to around late September.
That is essentially the extent of Monsoon season in Arizona. To sustain
themselves they're basic diet is insects. They sometimes eat
small animals such as lizards, small rodents and other small
toads or frogs.
Another odd thing about these unique toads, is the qualities of their venom and skin secretions. They have hallucinogenic qualities. People have been known to harvest these areas from a toad. They then dry and smoke them for that reason. We do not recommend or suggest that! It is reported by California Herps online that some states include these secretions as a controlled substance!
Another toad found in the same areas of AZ during Monsoon season is the Bufo punctatus. The common name is the red spotted toad. This species is just the opposite. It is very tiny, only about 3 inches long - at the largest. Its call is pretty strong, high pitched, and lasts about 10 seconds!
Its skin also gives off a venom to its enemies.
Taxonomically, it also has been more recently changed to reflect a more accurate description. Although usually still referred to as Bufo punctatus, it has been changed to Anaxyrus punctatus.
Its common name does describe it well, as it is covered in red spots. Its range is much more extensive than Bufo alvarius. It's found throughout the Southwest, and into Northwest Mexico.